Neptune is now considered the outermost planet, since Pluto was demoted to be a "minor planet" along with 23 others in 2007. However, Neptune may not be the outermost planet. There is a perturbation in the orbit of Neptune - a gravitational pull that remains unaccounted for. A possibility is that there is another ice giant well beyond Neptune and beyond our current technology to discover. Maybe you who will grow up to be astronomers and scientists will answer this question.

We had never seen Neptune as more than a traveling star until 1989 when Voyager 2, after spectacular success imaging and performing robotic research on Jupiter and Saturn, was given the go-ahead (i.e. money) by NASA to visit both Uranus and Neptune.

As I note elsewhere, the only reason this mission was even possible was because there was a planetary lineup of the four outermost planets of the solar system that was occurring. This event happens only once every 180+ years. We had the technology and we took advantage of it!

Voyager 2 reached Neptune on August 25, 1989. After the "disappointment" of Uranus which showed no great surface features, scientists were prepared for another disappointment. Here is what we saw! -- isn’t it beautiful?


Neptune



But let them talk for themselves.
Here is a video of the Voyager 2 encounter with Neptune.


OK. Wasn't that something! As Caroline Porco (the lady in the film says so eloquently), “Here at the farthest reaches of our Solar System, we see a world that looks like ours. It's beautiful, it’s blue and it has clouds”.

Of course the similarity ends there. Neptune is bloody cold. Even colder than on the highest mountains or south pole on Earth. I’d say it was colder than the North Pole but maybe in a few years, if we’re not really careful, and really change, the North Pole will have the weather attributes of Scotland, and you wouldn’t want that - rain all the time and everyone drinking Scotch. Well, maybe that’s not so bad. But, while a category 5 hurricane on Earth can produce winds of 150 miles an hour, and winds on Jupiter reach over 300 mph, on Neptune, the winds blow at more than 1000 mph -- all the time.

Voyager 2 has been our only spacecraft to visit Neptune, but a new journey is on the drawing boards. ___________ So boys and girls, cram and you may be one of those who will be part of the next mission. It will likely begin when you are graduate students and that is perfect timing for you. I merely hope to be around to see what you come up with.

As the film was made some 15 years ago, we've learned a lot more about the Ring Arcs that Caroline Porco and her team found. They, like the rings on Saturn are likely caused by material excreted (pulled) from the moon Triton or other moonlets we have not yet seen. The material may also be formed from cometary dust that like Triton, is captured by Neptune's gravity. Here is a great view of the ring arcs, with Neptune blocked out, you can see them clearly. In fact, they turn out, not to be arcs ,but full rings!

Neptune's Rings and Ringlets


After the flyby, we made a more detailed little video of the weather pattern on the planet. And this is what the clouds look like close up:

Neptune's Clouds

Also interesting in the film is the notion of Triton as a Planet. Well, it is a minor planet. It just orbits a giant planet and not the sun. We are learning constantly of new minor planets in our solar system. As I started out in this section, it's not your parents’ Solar System anymore. It's an extremely complex eco-system and with these voyages, we have barely scratched the surface of what we know of it. To spend three days filming as we transit a planet is surely not enough to give us definitive information as to how it came to be?

Just a reminder: You are looking at images six
billion miles from Earth! Think about that.

Here is a special image of Triton. Note the difference between the rocky cratered area and the relatively smooth valley. We can guess what caused this (one part is newer than the other and they merged), but until we send robotic craft to see more closely for ourselves, it simply is that, a guess!

Triton


Here is another high-resolution view of the smooth part of Triton. For reference, each pixel that makes up this image is 300m across.

Triton from 12 miles! - 3 billion miles away!!!

This is why I want you to be curious. As we learn more about our outermost planet, just as we are learning a lot about Jupiter and Saturn, we find the keys to unlock our knowledge of how we formed. We Humans, the Sun, the Planets, even life itself.

Here are some questions you can think about to start - Why are all the planets different? Why is Neptune blue and Uranus orangish? What really happened on Triton?

There are three people that I want you to know very well here although thousands of people worked on these projects.
Dr Edward Stone is a role model for all of us. He is considered the father of robotic spacecraft and has been the champion in getting funding, getting the right people and making the Voyager missions a reality. He has seen his share of disappointments - haven't we all? But every photograph and every mission and every discovery is because of Dr. Stone’s perseverance. Second, Dr. Brad Smith was one of the lead planetary scientists on Voyager, and is presently lead scientist for the Mars Phoenix Project. Dr. Smith is both businesslike and a man with great humility. The lesson is that success as a scientist, researcher, manager, or whatever you do in life - especially if you have success, should be coupled with a sense of your humanity and a sense of your humility. Dr. Caroline Porco a hero of mine - as are the many others - is presently lead scientist on the Cassini mission to Saturn and has her own site about Cassini. She is an example to women (and Men) everywhere. Note in the movie where she says what she was up against people telling her she was wrong about the rings on Neptune and how she proved THEY were wrong. Hold your dreams. Study hard and find GOOD role models.

Finally, as we left Neptune, Voyager took this one last photograph of the planet in the shadow of the sun:


Neptune South Pole